Upon its release, the album debuted at number 12 on the U.S. Billboard 200 chart, selling 59,000 copies in its first week. However, its initial sales fell below expectations and its five singles failed to achieve significant chart success. While it experienced initial low sales, Illmatic received positive reviews from most music critics upon its release and earned praise for its lyrical content, production, and Nas's lyricism. On January 17, 1996, the album was certified gold by the Recording Industry Association of America, and in 2001, it earned platinum certification after shipments of one million copies in the United States.

Since its initial reception, the album has been recognized by writers and music critics as a landmark album in East Coast hip hop. It contributed to the regional scene's artistic renaissance in New York, while marking an influential, stylistic change in hip hop at the time. Its influence on subsequent hip hop artists has been attributed to the album's production and Nas's rapping. Several writers have cited Illmatic as one of the quintessential hip hop recordings and one of the greatest hip hop albums of all time. In 2003, the album was ranked number 400 on Rolling Stone's list of the 500 greatest albums of all time.